A medieval surgeon repaired a broken bone with riveted copper plate

An unknown man got his axe arm badly injured in a battle. His humerus was found at excavations of Varnhem monastery in 1928, and is the only one of its kind in Sweden.
Interventions in the upper arm are difficult to do even for today's experts. It's easy for nerves and blood vessels to be damaged. Yet a medieval "surgeon" has managed to cover the injury to the man's arm bone, and also pin it with rivets; you can see three of them in the plate. We can also see that the man survived: new bone has been formed after the procedure.